I am getting ready to use an older model A90 that I bought on ebay. From what I can tell it is probably identical except for Grate size to the unit you are looking at. From what I can see it is a great unit with the traditional Keystoker aluminium pusher block and fan limit/timer type controls.
Since Keystoker is great about supplying parts I would say it is probably a good idea as long as it is not too far gone and is less than $700.
I have it disassembled for cleaning right now, so I can post some pics to see if it is the same as the unit you are looking at.